Simple shear testing of sensitive, very soft offshore clay for wide strain range

2009 ◽  
Vol 46 (11) ◽  
pp. 1277-1288 ◽  
Author(s):  
G. Lanzo ◽  
A. Pagliaroli ◽  
P. Tommasi ◽  
F. L. Chiocci
Keyword(s):  
Shear Modulus ◽  
Simple Shear ◽  
Damping Ratio ◽  
Soft Clay ◽  
Strain Range ◽  
Small Strain ◽  
Cyclic Shear ◽  
Wide Range ◽  
Equivalent Shear Modulus ◽  
Two Stages

Stiffness and damping properties of sensitive, very soft clay sediments of the Italian Adriatic continental shelf are determined by means of two series of cyclic simple shear tests (one with 12 stages and one with two stages). The apparatus used in this research is capable of investigating the stress–strain behaviour of the soil in a wide range of shear strains from about 0.0004% to 1%. Test results were expressed in terms of small-strain shear modulus (G0), normalized equivalent shear modulus (Geq/G0), and damping ratio (D) versus cyclic shear-strain amplitude (γc). These parameters were analyzed in the framework of existing literature by comparison with empirical correlations developed for onshore materials of different plasticity and, limited to G0, also for soft soils. The dependence of G0, Geq/G0–γc, and D–γc on factors such as void ratio, stress history, and loading cycles is analyzed and discussed.

Shear modulus and damping of soft Bangkok clays

2002 ◽  
Vol 39 (5) ◽  
pp. 1201-1208 ◽  
Author(s):  
Supot Teachavorasinskun ◽  
Pipat Thongchim ◽  
Panitan Lukkunaprasit
Keyword(s):  
Shear Modulus ◽  
Seismic Analysis ◽  
Damping Ratio ◽  
Soft Clay ◽  
Cyclic Stress ◽  
Large Strains ◽  
Cyclic Triaxial ◽  
Stress History ◽  
Load Frequency ◽  
Equivalent Shear Modulus

The shear modulus and damping ratio of undisturbed Bangkok clay samples were measured using a cyclic triaxial apparatus. Although abundant literature on this topic exists, selection of the most suitable empirical correlation for a seismic analysis cannot be done unless site specific data are obtained. The apparatus used in this research can measure the stress–strain relationships from strain levels of about 0.01%. The equivalent shear modulus measured at these strains was about 80% of the value obtained from the shear wave velocity measurements. The degradation curves of the equivalent shear modulus fell into the ranges reported in the literature, for clay having similar plasticity. The damping ratios varied from about 4–5% at small strains (0.01%) to about 25–30% at large strains (10%). The effects of load frequency and cyclic stress history on the shear modulus and damping ratio were also investigated. An increase in load frequency from 0.1 to 1.0 Hz had no influence on the shear modulus characteristic, but it did result in a slight decrease in the damping ratio. The effects of the small amplitude cyclic stress history on the subsequently measured shear modulus and damping ratio were almost negligible when the changes in void ratio were taken into account.Key words: soft clay, shear modulus, damping ratio, cyclic triaxial test, cyclic stress history.

scholarly journals Cyclic Loading Test for the Small-Strain Shear Modulus of Saturated Soft Clay and Its Failure Mechanism

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Zhende Zhu ◽  
Cong Zhang ◽  
Jun Wang ◽  
Peng Zhang ◽  
Duan Zhu
Keyword(s):  
Shear Stress ◽  
Shear Modulus ◽  
Effective Stress ◽  
Soft Clay ◽  
Small Strain ◽  
Triaxial Tests ◽  
Loading Test ◽  
Cyclic Shear ◽  
Small Strain Shear Modulus ◽  
Saturated Soft Clay

Small-strain shear modulus, G max , is a key evaluation index to study the dynamic characteristics of soil in geotechnical engineering. It is widely adopted to evaluate the stiffness of soft soil in soil dynamic engineering. In this paper, the cyclic triaxial tests and resonance column tests were carried out to explore the variation of G max of soft clay with respect to various confining stresses, cyclic shear stress ratios, pore pressures, and effective stress paths. Test results indicated that the effective stress decreased gradually with the increase of the cycle shear stress ratio. The failure points were mainly concentrated in a rectangular area, defined by the normalized effective stress from 0.56 to 0.64 and the normalized shear modulus from 0.72 to 0.78. Additionally, a short pause caused a small increase of 1-2% in G max as well as pore pressure. This study demonstrates that G max can be effectively used to characterize the failure of saturated soft clay in a more intuitive and convenient way, compared to the commonly used strain failure standards.

Shear modulus and damping ratio of sensitive Eastern Canada clays

2020 ◽  
Author(s):  
Mustapha Abdellaziz ◽  
Mourad Karray ◽  
Mohamed Chekired ◽  
Marie-Christine Delisle ◽  
Pascal Locat ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Damping Ratio ◽  
Small Strain ◽  
Eastern Canada ◽  
Equivalent Viscous Damping ◽  
Small Strain Shear Modulus ◽  
Undisturbed Samples ◽  
Wide Range ◽  
Linear Behaviour ◽  
Equivalent Viscous Damping Ratio

The shear modulus and equivalent viscous damping ratio of three sensitive clays from the sediments of the Champlain Sea were investigated using a combined triaxial simple shear apparatus. The tests were conducted on undisturbed samples and were carried out on a wide range of shear strain from about 0.001% to 1%. The values of the small strain shear modulus of the tested clays were further confirmed through a series of piezoelectric ring actuator and MASW tests. Although the shear modulus and damping ratio of the sensitive eastern Canada clays follow some classic literature models, the results show that the examined clays exhibited more linear behaviour. Such behaviour may be attributed to their highly structured nature compared to other clays. The compilation of available data on the shear modulus and damping ratio of several sensitive eastern Canada clays confirmed this trend and showed that some literature models might not be representative.

scholarly journals Very-small to large strain dynamic behaviour of unsaturated sand in a wide range of suction

2020 ◽  
Vol 195 ◽  
pp. 03002
Author(s):  
Ali Akbar Karimezadeh ◽  
Fardin Jafarzadeh ◽  
Anthony Kwan Leung ◽  
Adel Ahmadinezhad
Keyword(s):  
Transition Zone ◽  
Unsaturated Soil ◽  
Simple Shear ◽  
Dynamic Properties ◽  
Large Strain ◽  
Damping Ratio ◽  
Small Strain ◽  
Soil Parameters ◽  
Static And Dynamic Analysis ◽  
Wide Range

Shear modulus (Gmax at very small strain and G at large strain) and constraint modulus at very small strain (M) are important soil parameters for static and dynamic analysis in geotechnical applications. However, these dynamic properties of unsaturated soil are rarely reported. In this study, a cyclic simple shear apparatus was newly-modified for allowing both the shear and constrained moduli at both very small and large strains to be measured. Benders or ultrasonic sensors were embedded in an unsaturated soil sample for transmitting/receiving shear- and pressure-wave, respectively. Two very-small-strain tests were conducted to determine the Gmax, M and soil damping ratio of a sand for a wide range of suction covering from the boundary-effect, transition and residual zone of the water retention curve of the sand. In addition, six large-strain cyclic simple shear tests were carried out to investigate G. The test results showed that Gmax and M were approximately constant before reaching the air-entry value, but there was a significant increase in Gmax as the sand dried further. Yet, M dropped within the transition zone, and interestingly when the suction was beyond the residual value, M increased. M along the wetting path was higher than that along the drying path. The damping ratio, on the other hand, first reduced before reaching the air-entry value, but it increased at the transition zone and then decreased within the residual zone. At large strain, G/Gmax also increased as suction increased until reaching the residual zone, beyond which the normalised value show substantial decreased.

Dynamic Behavior of Sand/Rubber Mixtures. Part I: Effect of Rubber Content and Duration of Confinement on Small-Strain Shear Modulus and Damping Ratio

2011 ◽  
pp. 221-247 ◽  
Author(s):  
Anastasios Anastasiadis ◽  
Kostas Senetakis ◽  
Kyriazis Pitilakis ◽  
Chrysanthi Gargala ◽  
Iphigeneia Karakasi
Keyword(s):  
Shear Modulus ◽  
Dynamic Behavior ◽  
Damping Ratio ◽  
Small Strain ◽  
Rubber Content ◽  
Small Strain Shear Modulus

Dynamic Behavior of Sand/Rubber Mixtures. Part I: Effect of Rubber Content and Duration of Confinement on Small-Strain Shear Modulus and Damping Ratio

2011 ◽  
pp. 221-247
Author(s):  
Anastasios Anastasiadis ◽  
Kostas Senetakis ◽  
Kyriazis Pitilakis ◽  
Chrysanthi Gargala ◽  
Iphigeneia Karakasi
Keyword(s):  
Shear Modulus ◽  
Dynamic Behavior ◽  
Damping Ratio ◽  
Small Strain ◽  
Rubber Content ◽  
Small Strain Shear Modulus

scholarly journals Laboratory Studies of Small Strain Stiffness and Modulus Degradation of Warsaw Mineral Cohesive Soils

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1127
Author(s):  
Emil Soból ◽  
Katarzyna Gabryś ◽  
Karina Zabłocka ◽  
Raimondas Šadzevičius ◽  
Rytis Skominas ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Relative Error ◽  
High Reliability ◽  
Strain Range ◽  
Cohesive Soil ◽  
Small Strain ◽  
Empirical Models ◽  
Soil Behavior ◽  
Fundamental Parameters ◽  
Stiffness Characteristics

The shear modulus and normalized shear modulus degradation curve are the fundamental parameters describing soil behavior. Thus, this article is focused on the stiffness characteristic of 15 different Warsaw cohesive soli represented by the parameters mentioned above. In this research, standard resonant column tests were performed in a wide shear strain range, from a small one, where soil behaves like an elastic medium, to a medium one, where soil has an unrecoverable deformation. Collected data allows the authors to create empirical models describing stiffness characteristics with high reliability. The maximum shear modulus calculated by the proposed equation for Warsaw cohesive soil had a relative error of about 6.8%. The formula for normalized shear modulus estimated G/GMAX with 2.2% relative error. Combined empirical models for GMAX, and G/GMAX allow the evaluation of Warsaw cohesive soil’s shear modulus value in a wide shear deformation range, with a very low value of the relative error of 6.7%.

Shear Modulus and Damping Ratio of Sand–Gravel Mixtures Over a Wide Strain Range

2018 ◽  
Vol 23 (8) ◽  
pp. 1407-1440 ◽  
Author(s):  
Guoxing Chen ◽  
Zhenglong Zhou ◽  
Tian Sun ◽  
Qi Wu ◽  
Lingyu Xu ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Damping Ratio ◽  
Strain Range

Cyclic Simple Shear Apparatus for Low-Strain Soil Tests

1996 ◽  
Vol 1548 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Heather J. Miller ◽  
Pedro de Alba ◽  
Kenneth C. Baldwin
Keyword(s):  
Shear Modulus ◽  
Shear Strain ◽  
Simple Shear ◽  
Recovery Period ◽  
Triaxial Tests ◽  
Cyclic Shear ◽  
Aging Period ◽  
Direct Simple Shear ◽  
Fabric Evolution ◽  
Excess Pore Pressures

A testing system has been developed to study the behavior of saturated sand under low-level cyclic shearing strains. The system has been used to determine threshold shear strain levels for fabric destruction in sand aged for different time periods. The system includes a special soil chamber and a direct simple shear (DSS) machine. To impose very small shearing strains, the DSS machine was designed to apply and measure horizontal deformations as small as 0.0005 mm (2 × 10−5 inches). Data obtained to date support the results of previous investigators who performed triaxial tests on freshly deposited samples, indicating a threshold cyclic shear strain level of approximately 0.01 percent. At strains in excess of those levels, destruction of the sand fabric occurred, as evidenced by a reduction in shear modulus at low strain levels. Subsequent modest increases in shear modulus were observed after the specimens were allowed to recover for 24 hours and then tested again. During the recovery period, drainage valves were left open to allow for dissipation of excess pore pressures and for potential consolidation during the short aging period. The DSS system was found to work well for low strain measurements. Furthermore, since shear strains are measured directly under DSS conditions (as opposed to triaxial conditions), the DSS system shows much promise as a device for studying parameters that may influence threshold shear strain levels and fabric evolution and destruction in sands.

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